Froth flotation



March 27, 1934. R L T 1,952,727

FROTH FLOTATION Filed Oct. 26, 1929 INVENTOR 0//'l/er 6 Fa/s/on HIS ATTORNEY5 Patented Mar. 27, 1934 UNITED STATES morn FLOTATION Oliver 0. Ralston, Clarkdale, Ariz., assignor to United Verde Copper Company, Clarkdale, Arm, a corporation of Delaware Application October 26, 1929, Serial No. 402,635 -s Claims. (o 209-164) This invention relates to the control of froth in flotation and has for an object the provision of an improved method and apparatus for controlling froth formation and froth discharge and inhibiting the flotation of gangue and other'undesirable minerals.

According to the heretofore customary practices, the ore or mixture of minerals in the form of a pulp is subjected to agitation in the presence of frothing and mineral collecting agents in cells provided with overflow lips and having froth forming compartments adjacent the overflow lips. The froth produced contains the valuable minerals or a portion thereof and it is permitted to overflow into suitably disposed launders which are provided for the purpose of conducting the froth to suitable settling and thickening apparatus.

The ore being treated usually contains more than one mineral. capable of being floated by means of the reagents employed. In some cases, the ore contains two or more valuable minerals to be recovered and, usually, a readily floatableproportions and amounts. In some cases, the

flotation operations are conducted in stages in different ones of which the concentrate obtained is composed largely of different minerals.

The heretofore customary type of selective or differential flotation operation, therefore, re-

minerals contained in the ore, but since the amnity of a particular reagent may be greater for one mineral than for another it is at least theoretically possible to selectively float one mineral from a mixture through properly controlling the amount of reagent employed and/or the conditions under which the reagent is employed.

In spite of the different ailinities of various reagents for different minerals, it is virtually impossible in commercial operations to effect a complete separation of the different minerals in the primary cells even when the utmost care is exercised in adding the proper types and amounts of reagents. some of all of the minerals present in the pulp feed. This is due to the continuously varying quality of the feed, the practical impossibility of adding only the exact amount of reagent re- The primary froth usually contains or gradually, by some agency not under the direct control of the operator, be converted to an unsatisfactory operation producing a voluminous froth carrying excessive amounts of undesirable minerals and gangue. Such changes are usually caused by changes in the character of the ore, and correction can generally be made by adjustment of the amount or type of reagent being added. However, it is rather difficult to adjust the rate of addition and character of reagents to compensate for all changes in the character of the ore which affect the volume and mineral content of the froth.

In the operation of the usual flotation cell, a layer of froth several inches in thickness is pres- ,ent in the froth forming compartment. The bubbles forming the upper or surface portion of the froth layer and, particularly, those adjacent the source of agitation which produces the frothing effect, are generally larger than the remaining bubbles. The large bubbles and other fast forming bubbles adjacent the source of agitation appear to contain the larger proportion of gangue and undesirable minerals, but all bubbles contained in the froth are contaminated to some extent with undesirable minerals and gangue.

According to the method of the present invention, the froth is subjected to a type of treatment in the froth forming compartment as a result of which the mineral burdens of the froth overflowing may be controlled and regulated.

The apparatus of the invention comprises a flotation cell having in combination therewith means for treating the bubbles so as' to control The present invention provides for the elimi nation of undesirable matter from the froth by substituting a liquid of the desired composition for the contaminated liquid of the bubble fllms as formed; by destroying surface bubbles and transferring their mineral burdens to other bubbles; or -by'combined substitution of film substance and destruction of surface bubbles.- The invention valso contemplates the treatment of the bubbles of the froth with relatively small particles of mineral of the type for which the reagent or combination of reagents being used has the greater aflinity, to effect a substitution of such mineral particlesfor the undesirable minerals in influencing the rejection of undesirable minerals,

or particles of finely divided solid material alone or mixed with any suitable fluid. V

The force of the spray to be directed against the surface bubbles will. be determined by the efiect desired. For. example, if only a substitution of film substance is desired, a gentle or lowvelocity spray which will cause a minimum breaking of bubbles should be employed. If the surface bubbles are to be broken for the purpose of showering their mineral burdens upon the lower bubbles a high velocity spray should be employed. A. high velocity spray may be produced conveniently by means of a liquid atomizer consisting of an.

air nozzle connected to a source of supply of air under pressure, and a liquid supply nozzle hav ing .its .discharge opening disposed immediately 1 adjacent the discharge opening of the air nozzle.

A combined flhn substance substituting and bub-.

. ble breaking effect will be achieved when a high velocity spray containing aliquid is employed. This effect may be varied by varying the velocity of the spray and/or the volume of liquid contained therein.

The invention will be better understood from consideration of the following description in conjunction with the accompanying drawing, in which Fig. 1 is -a sectionalelevation of a flotation cell -having spraydevices disposed above the froth forming compartment; and

Fig. 2 is a side elevation of the apparatus shown in Fig. 1. a

The flotation can 10 is of the pneumatic type in which agitation of the pulp containing the desired reagents is effected by, means of downwardly directed air streams entering the pulp body through centrally disposed conduits 11. The flotation cell isprovided with fr h i 0mpartments 12 having overflow lips 13. Concentrate launders 14 are disposed adjacent the overflow lips 13 and are adapted to receive the froth passing over'the lips 13.

- A number of spray devices-or atomizers 17, each comprising a conduit 15 for supplyin gas under pressure, and a conduit 16 for supplying a liquid are disposed above each of the froth form ing compartments and connected to suitable sources of supply of gas under pressure and liquid (not shown). The atomizers may be adjustably mounted in order that the particles of fluid issuing therefrom may be directed against the surface of the froth at any desired point and/or at any desired angle. Suitable valves may be provided in the gas and liquid conduits for controlling the flow of gas and liquid.

Spray pipes 20 may be provided instead of or in addition to the atomizers 17. The spray pipes 20 extend transversely of the flotation cell and are connected to liquid supply headers 21 extend: ing longitudinally of the flotation cell. The spray pipes 20 are perforated in such a manner that flne streams or small droplets of liquid may bedirectedagains't the surface of the froth at points removed from the overflow lip. The rate of flow of liquid from the apertures in the pipes 20 maybe controlled by means of the valves 22 in the lines 23 which are connected to a source of supply (not shown).

'In .the operation of the apparatus of the invention, the froth formed rises to the surface of the pulp body in the froth forming compartments and passes over the overflow lips into the concentrate launders.

yWhena gentle sprayof pure water is applied.

for instance by means of spray pipes 20, the

water tends to pass downwardly through the layer of froth and in so doing it becomes substituted in the films of the bubbles with which it comes into contact for the liquid of which the films "were originally formed. The displaced liquid together with'the undesirable gangue and other materials contained therein: passes downwardly into the pulp body. I

When a high velocity spray capable of rupturing the surface bubbles is employed, the mineral burdens of the ruptured bubbles are showered downwardly upon the bubbles beneath the surface. When the released mineralscome into contact withthe lower bubbles, the particles of the mineral for which the reagent employed has the greater affinity will displaceparticles of the mineral or minerals for which the reagent has the lesser aifinity with the result that the de-- sired mineral will be concen'trated upon the lower bubbles which pass outwardly beyond the range of the fluid streams.

The effect of the application of finely divided minerals to the froth similar to the effect achieved by using a high velocity spray, that is,

a displacement and rejection of undesirable minerals is achieved. The mineral particles maybe applied in any desirable manner. A pulp of a high grade concentrate obtained in the particular operation involved may be used conveniently.

Solutions of reagents may be applied in any desired manner. Thus, limesolution may be sprayed gently over the surface of the froth to .p'roducethe combined effect of displacing the original film substance and causing an additional rejection, of pyrite, or the reagent may be ap-- plied in the form of a high velocity spray.

It may be desirable to provide merely for breaking some of the bubbles of the froth without incorporating anyextraneous material. In such cases a mechanical device capable of rupturing the bubbles, or a spray comprising an inert gas,

or finely divided solid may be employed.

The method of the present invention provides adesirable supplement'to reagent control, and

it may be utilized continuously or intermittently I as conditions warrant. The process maybe utilized continuously to supplement reagent control, permitting control of the amount and character of the froth without control of reagents.

It permits the use of a constant amount of necessitating close reagent and provides control of frothing conditions which arise as a result of changes in the character of the ore or the presence of unknown components in the reagents. Since the process of the invention provides frothcontrol, it may be utilized in conjunction with inferior reagents, and it permits the use of reagents which produce I tough froth.

with cleaning operations, close control of froth- I ing conditions in the rougher operations is unnecessary.

1. In a froth flotation process, the method of controlling the character of the froth which comprises directing a spray containing particles of solid matter against a portion of the froth in-the froth forming compartment of a flotation cell to effect a rejection of undesirable material contained therein.

2. In a froth flotation process, the method of controlling the character of the froth which comprises directing a spray containing particles of solid matter against the froth in the froth forming compartment of a flotation cell to break a portion of the bubbles forming the froth and shower their mineral burdens on other bubbles.

3. In afroth flotation process, the method of controlling the character of the froth which comprises spraying the upper surface of a layer of froth on' the surface of a body of pulp in a flotation cell with a liquid capable of entering the froth asa substitute for the bubble films, and

regulating the spraying operation to effect a sub stitution of the liquid of the spray for the bubble films.

4. In a froth flotation process, the method of controlling the character of the froth which comprises directing a liquid spray against a layer of froth in the froth forming compartment of a flotation cell to break bubbles comprising the upper portion; only of the "froth layer and shower their mineral burdens on bubbles comprising the lower portion of the froth layer, thereby to produce a froth of improved quality through replacement of undesired minerals in the lower bubbles with desired minerals released through breakage of the upper bubbles.

5. In a froth flotation process, the method of controlling the character of the froth which comprises directing a high velocity spray comprising minute particles of liquid against a layer of froth in the froth forming compartment of a flotation cell to break bubbles comprising the upper portion only of the froth layer and shower their mineral burdens on bubbles comprising the lower portion of the froth layer, thereby to produce a froth of improved quality through replacement of undesired minerals in the lower bubbles with desired minerals released through breakage of the upper bubbles.

6. In a flotation operation in which a mineral bearing froth is produced in a flotation cell and passes from the zone of production through a relatively quiescent zone onthe surface of a pulp body to a point at which it is removed from the cell, the improvement which comprises spraying the froth while passing through the relatively quiescent zone with a liquid capable of entering the froth as a substitute for the bubble films, and regulating the spraying operation to effect a substitution of the liquid of the spray for the bubble films.

v'7. In a flotation operation in which a mineral bearing froth is produced in a flotation cell and passes from the zone of production through a relatively quiescent zone on the surface of a pulp body to a point at which it is removed from the cell, the improvement which comprises applying to the froth while passing through the relatively quiescent zone an agent capable of entering the bubble structure to effect a rejection of undesirable matter contained therein, and regulating the operation to effect the rejection of undesirable matter from the froth.

- 8. In a froth flotation process, the step which comprises mechanically breaking the uppermost bubbles of a layer of froth ona bodyof pulp in a flotation cell without breaking the lowermost bubbles to shower the -mineral burdens of the uppermost bubbles upon the lowermost bubbles and thus cause a displacement of undesired minerals contained in the lowermost bubbles by means of minerals released from the uppermost bubbles through breaking.

q OLIVER C. RALSTON. 

